Seat weighing device

ABSTRACT

A seat weighing device which is not readily affected by the heat, as well as maintaining stable sensitivity of a load sensor. Four deformation resistors are disposed on a sensor plate with the same distance from the center of a fastening member. Furthermore, four openings are formed at positions near the fixing positions (mounting positions) for the two deformation resistors on the sensor plate. The formation of these openings, reduces the cross-sectional area at positions where the openings have been formed on the sensor plate, and thus, the sensor plate readily flexes (deforms) at a position around the fixing positions for the deformation resistors. This enables the deformation resistors, to measure the load in a sure manner.

BACKGROUND

The present invention relates to a seat weighing device, provided to aseat for a vehicle, for weighing a seat including the weight of apassenger on the seat.

As safety devices for improving safety of a passenger in an automobile,a seat belt device, an airbag device, and the like, are known. Recently,development of control devices for controlling these safety devicescorresponding to the weight and the attitude of the passenger is beingundertaken in order to further improve the performance of the seat beltor the airbag. For example, the control device adjusts the amount of theinflation gas or the inflation speed of the airbag, or adjusts thepretension of the seat belt, corresponding to the weight and theattitude of the passenger. Accordingly, there is the need to weigh thepassenger on the seat, as well as the position of the center of gravityof the passenger.

In order to meet such a demand, a low-cost seat weighing device has beenproposed for precisely weighing the seat such as, for example, JapaneseUnexamined Patent Application Publication No. 2001-041813 (herebyincorporated by reference herein in its entirety).

FIGS. 7(A)-7(B) show partial views of the front portion of the seatweighing device disclosed in the aforementioned Japanese UnexaminedPatent Application Publication No. 2001-041813, wherein FIG. 7(A) is adisassembled perspective view thereof, FIG. 7(B) is a cross-sectionalfront view of a pin-bracket portion thereof, and FIGS. 8(A), 8(B), 8(C),and 8(D) show partial views of the front portion of the seat weighingdevice shown in FIGS. 7(A)-(B), wherein FIG. 8(A) is a plan viewthereof, FIG. 8(B) is a cross-sectional view along the longitudinaldirection thereof, FIG. 8(C) is a cross-sectional view taken along lineC-C in FIG. 8(B), and FIG. 8(D) is a cross-sectional view taken alongline D-D in FIG. 8(B).

As shown in FIGS. 7(A) and 7(B), and FIGS. 8(A) and 8(B), a conventionalseat weighing device 9 comprises a long and narrow base 21 serving as abase component thereof. The base 21 is to be mounted on the vehiclebody, extending long in the longitudinal direction thereof, and the base21 formed of a U-shaped pressed steel frame is mounted with the openside facing upward, wherein both the left and right ends of a bottomplate 21 c of the base are bent perpendicular thereto so as to form sideplates 21 a and 21 a′ erected on the bottom plate 21, as shown in FIGS.8(C) and 8(D).

Each of the side plates 21 a and 21 a′ of the base 21 include two pinopenings 21 e and 21 g arrayed in the longitudinal direction of the base21. Note that the pin openings 21 e and 21 g are formed on both the sideplates 21 a and 21 a′ so as to face the corresponding pin openings. Thepin openings 21 e closer to the front end are formed at positions around⅛ of the entire length of the base 21 away from the front portion of thebase 21 along the longitudinal direction thereof. The pin openings 21 eare formed in the shape of a slot with the major axis perpendicular tothe bottom plate 21 c as shown in FIG. 7(A). The ends of a bracket pin27 are inserted into the slots 21 e. Furthermore, retainers 33 aresecured to both the left and right ends of the bracket pin 27. Thebracket pin 27 is fixed to the slot 21 e by the retainers 33.

However, the bracket pin 27 is inserted into the slots 21 e with a gapin both the horizontal and vertical directions, i.e., the bracket pin 27is not in contact with the inner faces of the slots 21 e in the normalstate. However, in the event that an excessive load is applied to theseat weighing device 9 (specifically, the pin bracket 25), the bracketpin 27 moves downward and comes into contact with the lower edge of theslot 21 e, and accordingly, the excessive load does not affect a loadsensor 50 disposed on a sensor plate (spring member) 51. That is to say,the bracket pin 27 and the slots 21 e form a part of the restrictingmechanism for restricting the maximal load applied to the sensor plate51. Note that the bracket pin 27 generally serves as a member fortransmitting the weight of the seat applied to the pin bracket 25 to anarm 23.

Furthermore, the pin openings 21 g are formed at positions somewhat awayfrom the slot 21 e toward the middle portion of the base 21(specifically, at positions approximately {fraction (1/10)} of theentire length of the base 21 away from the slot 21 e toward the middleportion). A base pin 31 passes through the pin openings 21 g. The basepin 31 is disposed so as to be introduced between both the left and theright side plates 21 a and 21 a′ of the base 21. Furthermore, retainers33 are secured to both the left and right ends of the base pin 31 so asto fix the base pin 31 to the base 21. Note that the base pin 31 servesas a shaft around which the arm 23 is turned.

The arm 23 is formed of an elastic member, and is disposed within thebase 21. The bottom plate of the arm 23 is formed in the shape whereinone end thereof closer to the middle portion of the base 21 is formed inthe shape of “V” extending in the horizontal direction (V-shaped portion23 h), and the other end thereof closer to the front end of the base 21is formed in the shape of a rectangle. Both the left and the right endsof a half part of the arm 23 closer to the front end of the base 21 arebent upward perpendicular to the bottom plate of the arm 23 so as toform side plates 23 a. On the other hand, the V-shaped portion 23 h isformed of a simple flat plate. The side plates 23 a are disposed withinthe base 21 along the side plates 21 a thereof. Note that the sideplates 23 a and 21 a are disposed with a gap therebetween.

Each of the side plates 23 a of the arm 23 include two pin openings 23 cand 23 e, as well. The bracket pin 27 passes through the pin openings 23c formed closer to the front end of the base 21. The bracket pin 27hardly exhibits any sliding movement on the pin openings 23 c. On theother hand, the base pin 31 passes through the pin openings 23 e formedcloser to the middle portion of the base 21. The base pin 31 serves as acenter around which the arm 23 is turned, and accordingly, the base pin31 exhibits sliding movement on the pin openings 23 e corresponding toturning of the arm 23. Note that doughnut-shaped spacers 35 are fit toboth the ends of the base pin 31 between the side plate 21 a of the base21 and the side plate 23 a of the arm 23.

The V-shaped portion 23 h of the arm 23 is formed with generally half ofthe entire length of the arm 23. The left and right ends of the V-shapedportion 23 h are forked so as to extend toward the middle portion of thebase 21 in the longitudinal direction, and are formed narrow closer tothe middle portion. Action portions 23 j at the tips of the V-shapedportion 23 h of the arm 23 are introduced between a blade 41 a of anupper half arm 41 and a blade 42 a of a lower half arm 42. The lowerface of the main body of the upper half arm 41 and the upper face of themain body of the lower half arm 42, formed flat, are fixed to a sensorplate 51 so as to be fit flush with the surface thereof with a screw 43.

Upon a load being applied to the pin bracket 25, the load is applied tothe arm 23, and as a result, the arm 23 is slightly turned (with themaximal turning angle of 5°) so as to transmit the load to the sensorplate 51 from the action portions 23 j through the upper and lower halfarms 41 and 42. As shown in FIG. 9, the load sensor 50 is mounted on thesensor plate 51. Of four deformation resistors forming the load sensor50, two deformation resistors 54 a and 54 b thereof are disposed so asto detect the tensile strain, and the other two deformation resistors 54c and 54 d are disposed so as to detect the compressive strain. Notethat these four deformation resistors 54 a, 54 b, 54 c, and 54 d, aredisposed in that order along the line passing through the center of thesensor plate 51 in the longitudinal direction thereof.

Furthermore, the aforementioned four deformation resistors 54 a, 54 b,54 c, and 54 d, are electrically connected so as to form a bridgecircuit. The pin bracket 25 is formed generally in a cross-sectionalshape of “U” with the open side facing downward as shown in FIG. 8(C).Note that the pin bracket 25 is formed with length of around {fraction(1/20)} of the base 21 in the longitudinal direction, which is not solong. Furthermore, the upper face 25 a of the pin bracket 25 is formedflat so as to mount a seal rail 7. Note that the seat rail 7 is fixedlyconnected to the pin bracket 25 with screws or the like. Furthermore,the sensor plate 51 is fixed to a column 63 erected on the middleportion of the bottom plate 21 c of the base 21 with nuts 68, andfastening members 69 such as screws, bolts, or the like.

Both left and right side plates 25 b of the pin bracket 25 extenddownward, and both the lower ends thereof are bent inward. The sideplates 25 b are disposed so as to be introduced between the side plates23 a and 23 a′ of the arm 23 with a predetermined gap. Furthermore, theside plates 25 b include pin openings 25 c. Note that the bracket pin 27passes through the pin openings 25 c. The pin openings 25 c are formedwith a greater size than the diameter of the bracket pin 27. The gapsbetween the pin openings 25 c and the bracket pin 27 absorb the marginof error in the size of the seat and vehicle, and unintendeddeformation.

A spring plate 29 is disposed so as to be introduced between both theleft and right side plates 25 b of the pin bracket 25 and both the leftand right side plates 23 a of the arm 23. The spring plate 29 has aspring seat including openings for fitting the bracket pin 27 with agap. The spring plate 29 forms a centering mechanism for forcing the pinbracket 25 toward middle portion. Such a centering mechanism forces thepin bracket 25 to be slidably positioned at a position as close to themiddle as possible.

With the seat weighing device 9, the seal rail 7, pin bracket 25, thearm 23, the base 21, the seat bracket 11, and the like, form aconnecting mechanism between the seat and the vehicle.

With the seat weighing device disclosed in Japanese Unexamined PatentApplication Publication No. 2001-041813, recesses are formed at theregions between a pair of the deformation resistors 54 a and 54 c, andbetween the other pair of the deformation resistors 54 b and 54 d,forming the load sensor 50, on the sensor plate 51, so that the sensorplate 51 readily flexes (deforms) around these regions, therebystabilizing the sensitivity of the load sensor, but there is the need toperform precision machining for the sensor plate, leading to a problemof high costs.

On the other hand, the four deformation resistors 54 a, 54 b, 54 c, and54 d, are disposed in that order along the line passing through thecenter of the sensor (i.e., the center of the fastening member 69) inthe longitudinal direction of the sensor plate 51, and accordingly, arenot disposed at positions with the same distance from the center of thesensor. Accordingly, in the event that rapid change in the temperatureof the surroundings occurs, the four deformation resistors 54 a, 54 b,54 c, and 54 d, may not immediately reach the same temperature due toheat transmitted to the sensor plate 51 through the fastening member 69secured at the middle portion of the sensor, leading to a problem thatthe bridge formed of the four deformation resistors may lose balancethereof.

SUMMARY

The present invention has been made in order to solve theabove-described problems, and accordingly, it is an object thereof toprovide a seat weighing device which is not readily affected by heatwhile maintaining stable sensitivity of the load sensor with low costs.

In order to solve the above-described problems, a seat weighing deviceaccording to an embodiment of the present invention comprises a loadsensor for weighing a seat for a vehicle including the weight of apassenger on the seat; a load transmitting member for transmitting theweight of the seat to the load sensor; and a base for supporting theload sensor and the load transmitting member, wherein the load sensor ismounted on a sensor plate where the load is transmitted, and the sensorplate includes means provided at a position near the mounting positionfor the load sensor, for causing the sensor plate to readily deformaround the mounting position for the load sensor.

Furthermore, with a seat weighing device according to an embodiment ofthe invention, the means is formed of a predetermined number of openingsformed at positions near the mounting positions for the load sensor onthe sensor plate.

Furthermore, with a seat weighing device according to another embodimentof the present invention, the sensor plate is fixed to the base with afastening member, and the load sensor includes a predetermined number ofdeformation resistors fixed on the sensor plate with the same distancefrom the fastening member secured to the sensor plate.

With the seat weighing device having such a configuration according toembodiments of the present invention, the sensor plate includes means ata position near the load-sensor mounting position on the sensor platefor causing the sensor plate to readily deform around the load-sensormounting position, and thus, this causes the sensor plate to readilyflex (deform) around the load-sensor mounting position. Accordingly,deformation of the sensor plate exhibits a concentration at positionsaround the load-sensor mounting position, thereby stabilizing thesensitivity of the load sensor. This enables the load sensor to measurethe load in a sure manner.

According to another embodiment of the present invention, theaforementioned means for causing the sensor plate to readily deformaround the load-sensor mounting position is formed of a predeterminednumber of openings formed at positions near the load-sensor mountingposition on the sensor plate, thereby improving durability against thetorsional stress applied to the sensor plate, and thus, the measurementof the load can be made with the load sensor in a sure manner, whilemaintaining the simple configuration of the aforementioned means.

Furthermore, according to an embodiment of the present invention, apredetermined number of deformation resistors are disposed on the sensorplate with the same distance from the fastening member thereon, andaccordingly, the predetermined number of deformation resistors are notnon-uniformly affected by the heat transmitted to the sensor platethrough the fastening member due to rapid change in the temperature,thereby preventing the bridge formed of the predetermined number ofdeformation resistors from losing balance. Thus, more precise weight ofthe seat can be obtained.

An occupant detection device, according to another embodiment of theinvention, comprises a load sensor for weighing a seat for a vehicleincluding the weight of a passenger on the seat, a load transmittingmember for transmitting the weight of said seat to said load sensor, anda base for supporting said load sensor and said load transmittingmember. The load sensor is mounted on a sensor plate where said load istransmitted, and the sensor plate includes means provided at a positionnear the mounting position for said load sensor, for causing said sensorplate to readily deform around said mounting position for said loadsensor.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 is a perspective view which shows a seat weighing deviceaccording to an embodiment of the present invention.

FIGS. 2(A), 2(B), and 2(C) show views of the seat weighing device shownin FIG. 1, wherein FIG. 2(A) is a plan view thereof, FIG. 2(B) is across-sectional view taken long line A-A in FIG. 2(A), and FIG. 2(C) isa right side view thereof.

FIGS. 3(A) and 3(B) shows views of a part of the seat weighing deviceshown in FIG. 1, wherein FIG. 3(A) is a perspective view which shows aload transmitting portion, and FIG. 3(B) is a perspective view whichshows a load sensor portion.

FIGS. 4(A) and 4(B) shows disassembled views of the load transmittingportion and the load sensor portion shown in FIGS. 3(A) and 3(B),wherein FIG. 4(A) is a disassembled perspective view which shows theload transmitting portion, and FIG. 4(B) is a disassembled perspectiveview which shows the load sensor portion.

FIG. 5 is a plan view which shows the sensor plate including apredetermined number of openings, employed for an arrangement exampleshown in FIG. 1

FIGS. 6(A) and 6(B) show means for causing the sensor plate and thedeformation resistors fixed thereon to readily deform in a case of anarrangement including an arm having two action portions, wherein FIG.6(A) is a plan view which shows an example thereof, and FIG. 6(B) is aplan view which shows another example thereof.

FIGS. 7(A) and 7(B) show partial views of the front portion of aconventional seat weighing device wherein FIG. 7(A) is a disassembledperspective view thereof, and FIG. 7(B) is a cross-sectional view asviewed from the front side.

FIGS. 8(A), 8(B), 8(C) and 8(D) show partial views of the front portionof the seat weighing device shown in FIGS. 7(A) and 7(B), wherein FIG.8(A) is a plan view thereof, FIG. 8(B) is a longitudinal cross-sectionalview thereof, FIG. 8(C) is a cross-sectional view taken along line C-Cin FIG. 8(B), and FIG. 8(D) is a cross-sectional view taken along lineD-D in FIG. 8(B).

FIG. 9 is a partial perspective view which shows the load sensor portionof a conventional seat weighing device.

DESCRIPTION

Hereinafter, embodiments of the present invention will be described withreference to the attached drawings. Note that the same components aswith the seat weighing device, shown in FIGS. 7(A) through FIG. 9,disclosed in Japanese Unexamined Patent Application Publication No.2001-041813 are denoted by the same reference numerals, and detaileddescription thereof will be omitted.

As shown in FIG. 1, and FIGS. 2(A), 2(B), and 2(C), the seat weighingdevice 9 comprises load transmitting portions 70 on the front side andthe rear side, and a load sensor portion 71 disposed between theaforementioned load transmitting portions 70, serving as separatecomponents. Accordingly, the base 21 comprises two load transmissionbases 21α for the load transmitting portions 70 on the front side andthe rear side in the longitudinal direction, and the load sensor base21β on the load sensor portion 71, serving as separate components. Notethat the load transmitting bases 21α and the load sensor base 21β areformed in a cross-sectional shape of “U” in the same way as with thebase 21 disclosed in Japanese Unexamined Patent Application PublicationNo. 2001-041813. In this case, while the two load transmitting bases 21αon the front side and the rear side are formed with generally the sanesize as with the base 21 disclosed in Japanese Unexamined PatentApplication Publication No. 2001-041813, the load sensor base 21β isformed such that the bottom thereof is positioned at a shallow depth ascompared with the load transmitting bases 21α. Furthermore, as shown inFIG. 2(B), both the front and rear ends of the bottom plate 21 c of theload sensor base 21β are mounted on the bottom plate 21 c of the twoload transmitting bases 21α on the front and rear sides, respectively.In this state, the side plates 21 a and 21 a′ of the load transmittingbases 21α, and the side plates 21 a and 21 a′ of the load sensor base21β, are connected with connecting members 76 such as four bolts or thelike, whereby the entire base 21 is formed. Note that the aforementionedbase 21 is formed such that the side plates 21 a and 21 a′ of the twoload transmitting bases 21α, and the side plates 21 a and 21 a′ of theload sensor base 21β, are positioned at the same height.

As shown in FIG. 3(A) and FIG. 4(A), the load transmitting base 21α ofthe load transmitting portion 70 on the rear side includes the pinbracket 25 for receiving the seat weight, and the arm 23 for receivingthe seat weight from the pin bracket 25, therewithin. While the arm 23is formed of an elastic member, the arm 23 does not include a V-shapedportion having the two action portions 23 j, but includes a single tipserving as the action portion 23 j, unlike the arm 23 disclosed inJapanese Unexamined Patent Application Publication No. 2001-041813. Theaforementioned single action portion 23 j is mounted to the sensor plate51 through the upper and lower half arms 41 and 42 so as to transmit theseat weight from the arm 23 to the sensor plate 51 through the half arms41 and 42, as shown in FIG. 1, and FIGS. 2(A) and (B).

The arm 23 has the same configuration as with the arm 23 disclosed inJapanese Unexamined Patent Application Publication No. 2001-041813,except for the above-described configuration, wherein the arm 23 isturnably supported by the side plates 21 a and 21 a′ of the base 21through the base pin 31. Furthermore, the bracket pin 27 passes throughthe side plates of the arm 23 so as to transmit the seat weight from thepin bracket 25 to the arm 23 through the bracket pin 27.

Furthermore, the pin bracket 25 is turnably supported by the base pin 31so as to transmit the seat weight applied to the pin bracket 25 to thebracket pin 27, unlike the pin bracket 25 disclosed in JapaneseUnexamined Patent Application Publication No. 2001-041813.

The load transmitting portion 70 on the front side has the sameconfiguration as with the load transmitting portion 70 on the rear sidedescribed above, symmetrically in the longitudinal direction.

Furthermore, as shown in FIG. 2(A) and FIG. 5, with the seat weighingdevice 9 according to an embodiment of the present invention, apredetermined number (four in a example shown in the drawing) ofdeformation resistors 54 a, 54 b, 54 c, and 54 d, are fixed (mounted)onto the sensor plate 51 so as to be positioned on a single circle withthe center O of the sensor (the center of the fastening member 69) asthe center of the circle. That is to say, the four deformation resistors54 a, 54 b, 54 c, and 54 d, are disposed with the same distance from thecenter O of the sensor (the center of the fastening member 69). The seatweighing system 9 may include a different, suitable number of strainresistors, other than four.

Furthermore, the sensor plate 51 includes a predetermined number (fourin an example shown in the drawing) of openings 72, 73, 74, and 75, nearthe fixing positions (mounting positions) for the two deformationresistors 54 b and 54 c. The aforementioned openings 72, 73, 74, and 75,are formed on lines α and β, which pass through the fixing positions ofthe two deformation resistors 54 b and 54 c, parallel to the axis of thebending moment applied to the sensor plate 51 due to the loadtransmitted through the upper and lower half arms 41 and 42, so as tointroduce the two deformation resistors 54 b and 54 c therebetween.These openings 72, 73, 74, and 75, reduce the cross-sectional area ofthe sensor plate 51 along the lines α and β, and thus the sensor plate51 readily flexes (deforms) at the fixing positions for the deformationresistors 54 a, 54 b, 54 c, and 54 d. Thus, measurement of the load canbe performed with the deformation resistors 54 a, 54 b, 54 c, and 54 d,in a sure manner. That is to say, with the embodiment according to thepresent invention, the aforementioned openings 72, 73, 74, and 75, formmeans for allowing the sensor plate to readily deform at mountingposition of the load sensor. The sensor plate 51 may include more orless than four holes, as suitable.

Note that an arrangement may be made wherein recesses are formed on theedges γ, δ, ε, and ξ (the edges δ and ξ are denoted by dotted lines asan example. Unshown edges γ and ε are formed in the same way) on thesensor plate 51, where the aforementioned lines α and β pass through, soas to reduce the cross-sectional area of the sensor plate 51 along thelines α and β so that the sensor plate 51 readily flexes (deforms),instead of formation of the openings 72, 73, 74, and 75. However, inthis case, the edges γ, δ, ε, and ξ, have been cut off from the sensorplate 51, and accordingly, the sensor plate 51 is susceptible totorsional stress. This leads to deterioration in precision formeasurement of the load. On the other hand, with an arrangementincluding the openings 72, 73, 74, and 75, the edges γ, δ, ε, and ξ,have not been cut off from the sensor plate 51, and accordingly, thesensor plates 51 has sufficient durability against torsional stress,thereby improving the precision for measurement of the seat load withthe deformation resistors 54 a, 54 b, 54 c, and 54 d.

Furthermore, as shown in FIG. 2(B), the fastening member 69 is insertedso as to pass through the opening of the bottom plate 21 c and theopening of the sensor plate 51 from the lower side of the bottom plate21 c of the load sensor base 21β of the load sensor portion 71 so as tobe fixed by the nut 68, whereby the sensor plate 51 is fixed to the loadsensor base 21β. In this case, the load sensor base 21β is formed with ashallower bottom for mounting the fastening member 69 as compared withthe load transmitting bases 21α, and accordingly, even in the event thatthe fastening member 69 is fixed so as to protrude downward from thebottom plate 21 c of the load sensor base 21β, the irregularities in theheight are suppressed over the entire base 21.

The seat weighing device 9 according to an embodiment of the presentinvention has the same configuration as with the seat weighing devicedisclosed in Japanese Unexamined Patent Application Publication No.2001-041813 shown in FIG. 7 through FIG. 9 described above, except forthe above-described configuration.

With the seat weighing device 9 according to an embodiment of thepresent invention, the sensor plate 51 includes four openings 72, 73,74, and 75, at positions near the two deformation resistors 54 b and 54c, thereby reducing the cross-sectional area of the sensor plate 51 nearthe mounting position for the load sensor. Accordingly, the sensor plate51 readily flexes (deforms) around the mounting position for the loadsensor, and accordingly, deformation of the sensor plates 51 exhibits aconcentration at positions around the load-sensor mounting position,thereby stabilizing the sensitivity of the load sensor 50 whileimproving durability against the torsional stress applied to the sensorplate. Thus, the measurement of the load applied to the seat can be madewith the load sensor in a sure manner.

Furthermore, the seat weight transmitted to the arm 23 is transmitted tothe sensor plate 51 through the single action portion 23 j. As describedabove, the arm 23 does not include the V-shaped portion, but includesthe single action portion 23 j, thereby suppressing irregularities intransmission of the load. Accordingly, the arm 23 may be manufacturedwith low precision as compared with the arm 23 including the V-shapedportion. Thus, the arm 23 can be easily manufactured with low costs.

Furthermore, the base 23 is formed of the two load transmitting bases21α and the load sensor base 21β, serving as separate components,thereby enabling sub-assembly of the load transmitting portion 70 andthe load sensor portion 71, separately one from another. Thisfacilitates assembly of the seat weighing device 9. Furthermore, theload sensor base 21β of the load sensor portion 71 is formed with ashallow bottom as compared with the load transmitting base 21α, i.e.,the load sensor base 21, is formed with smaller height than with theload transmitting base 21α, thereby suppressing irregularities in theheight over the entire set weight measurement device 9 including thebase 21, even if the fastening member 69 protrudes from the bottom plate21 c of the load sensor base 21β.

Furthermore, the four deformation resistors 54 a, 54 b, 54 c, and 54 d,are disposed with the same distance from the center of the sensor (thecenter of the fastening member 69), and accordingly, the fourdeformation resistors 54 a, 54 b, 54 c, and 54 d, are not non-uniformlyaffected by the heat transmitted to the sensor plate through thefastening member due to rapid change in the temperature, therebypreventing the bridge formed of the four deformation resistors 54 a, 54b, 54 c, and 54 d, from losing balance. Thus, more precise weight of theseat can be obtained.

The seat weighing device 9, according to an embodiment of the invention,has the same functions and advantages as with the seat weighing devicedisclosed in Japanese Unexamined Patent Application Publication No.2001-041813 shown in FIG. 7 through FIG. 9 described above, except forthe above-described functions and advantages.

Note that while description has been made regarding the arrangementexample wherein the arm 23 for transmitting the load to the load sensor50 has only a single action portion 23 j, the present invention is notrestricted to the above-described arrangement. Rather, according toanother embodiment of the invention, the seat weighing device 9 mayinclude an arm 23 comprising a V-shaped portion having two actionportions 23 j.

FIG. 6 shows an example of the sensor plate 51 including fourdeformation resistors 54 a, 54 b, 54 c, and 54 d, fixed thereon, andfour openings 72, 73, 74, and 75, serving as means for allowing thesensor plate 51 to readily deform, for being employed for the arm 23including the two action portions 23.

As shown in FIG. 6, the sensor plate 51 according to the present exampleis formed generally in a shape of “T” as with the sensor plate 51disclosed in the Japanese Unexamined Patent Application Publication No.2001-041813.

Furthermore, the four deformation resistors 54 a, 54 b, 54 c, and 54 d,are fixed to the horizontal part of the T-shaped sensor plate 51. Inthis case, supported centers O₁, and O₂, on the sensor plate 51, wherethe sensor plate 51 is supported by the upper and lower half arms 41 and42 (i.e., the action portions where the load is applied from the halfarms 41 and 42, to the sensor plate 51), and the center O of the loadsensor 50 (i.e., the center of the fastening member 69), are arrayed ona single line η while the two deformation resistors 54 a and 54 b aredisposed between the center O and the supported center O₁ on the line η,and the other two deformation resistors 54 c and 54 d are disposedbetween the center O and the supported center O₂ on the line η.

Furthermore, with the arrangement example shown in FIG. 6, two pairs ofopenings 72 and 73, and 74 and 75, are formed on lines α and β on thesensor plate 51 so as to surround the two deformation resistors 54 b and54 c, in the same way as with the above-described arrangement example,and in addition, the other two pairs of openings 77 and 78, and 79 and80, are further formed on lines θ and ι, parallel to the aforementionedlines α and β on the sensor plate 51 so as to surround the twodeformation resistors 54 d and 54 a. The arrangement shown in FIG. 6 hasgenerally the same functions and advantages as with the above-describedarrangement example.

While description has been made regarding the arrangement examplewherein the base 23 is formed of three separate components, to thepresent invention is not restricted to the aforementioned arrangement,rather, the present invention may be applied to the seat weighing device9 including the base 23 formed of a single member as with the seatweighing device 9 disclosed in the aforementioned Japanese UnexaminedPatent Application Publication No. 2001-041813.

The seat weighing device according to the present invention is mountedto a seat of a vehicle where height is restricted, and is suitably usedfor weighing a seat including the weight of a passenger on the seat.

Japan Patent Application 2003-184967, filed Jun. 27, 2003 including thespecification, drawings, claims and abstract, is incorporated herein byreference in its entirety. Japan Patent Application 2004-034522, filedFeb. 12, 2004 including the specification, drawings, claims andabstract, is incorporated herein by reference in its entirety.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention is to be defined as set forth in the followingclaims.

1. A seat weighing device comprising: a load sensor for weighing a seatfor a vehicle including the weight of a passenger on the seat; a loadtransmitting member for transmitting the weight of said seat to saidload sensor; and a base for supporting said load sensor and said loadtransmitting member; wherein said load sensor is mounted on a sensorplate where said load is transmitted; and wherein said sensor plateincludes means provided at a position near the mounting position forsaid load sensor, for causing said sensor plate to deform around saidmounting position for said load sensor.
 2. The seat weighing device ofclaim 1, wherein said means is formed of a predetermined number ofopenings formed at positions near said mounting positions for said loadsensor on said sensor plate.
 3. The seat weighing device of claim 1,wherein said sensor plate is fixed to said base with a fastening member,and wherein said load sensor includes a predetermined number ofdeformation resistors fixed on said sensor plate equally spaced fromsaid fastening member secured to said sensor plate.
 4. An occupantdetection device comprising: a load sensor for weighing a seat for avehicle including the weight of a passenger on the seat; a loadtransmitting member for transmitting the weight of said seat to saidload sensor; and a base for supporting said load sensor and said loadtransmitting member; wherein said load sensor is mounted on a sensorplate where said load is transmitted; and wherein said sensor plateincludes means provided at a position near the mounting position forsaid load sensor, for causing said sensor plate to readily deform aroundsaid mounting position for said load sensor.
 5. The occupant detectiondevice of claim 4, wherein the means comprises openings in the sensorplate.
 6. The occupant detection device of claim 4, wherein the loadsensor includes resistors fixed on the sensor plate.
 7. The occupantdetection device of claim 6, wherein the resistors are configured to beuniformly affected by heat transmitted to the sensor plate.
 8. Anoccupant detection device comprising: a load sensor for weighing a seatfor a vehicle including the weight of a passenger on the seat; a loadtransmitting member for transmitting the weight of said seat to saidload sensor; and a base for supporting said load sensor and said loadtransmitting member; wherein said load sensor is mounted on a sensorplate where said load is transmitted; and wherein said sensor plateincludes openings provided at a position near the mounting position forsaid load sensor, wherein the openings are positioned to permit saidsensor plate to deform around said mounting position for said loadsensor.
 9. The occupant detection device of claim 8, wherein theopenings are configured to reduce the cross-sectional area on the sensorplate at the position of the openings.